Discharge lamp flashing circuit



March 30, 1954 A. D. COOPER ETAL 2,673,943

DISCHARGE LAMP FLASHING CIRCUIT Filed Aug. 21. 1950 Inven=lrorsz An chong DonaLd Cooper. Evan Herberi Netson, Ani'hong Ha dn WILLOLEQb by M rf TFieir A tflrornes.

Patented Mar. 30, 1954 DISCHARGE LAMP FLASHING CIRCUIT Anthony D. Cooper, Wembley, Evan H. Nelson, Harrow Weald, and Anthony H. Willoughby, Rickmansworth, England, assignors to General Electric Company, a corporation of New York Application August 21, 1950, Serial N 0. 180,654

Claims priority, application Great Britain September 6, 1949 4 Claims. 1

This invention relates generally to arrangements for operating an electric discharge lamp to produce repeated flashes of light by alternately striking and extinguishing the discharge in the lamp. Arrangements of this type may be used, for example, for code signalling, for lighthouse warning, or for airport beacon flashing.

The lamps most often used in combination with such arrangements are high pressure metal vapor electric discharge lamps, the usual metal bein mercury. With such lamps, the discharge may readily be struck at a comparatively low voltage when the lamp is cold, since the vapor pressure within it is then relatively low owing to condensation of the metal. In operation, however, the filling is at a relatively high pressure, often in excess of half an atmosphere, and the striking voltage required is then much higher so that reliable striking of the discharge is more difficult to effect.

In arrangements for cod signalling by means of discharge lamps, flashes are often produced at such a rate that the'filling remains at a high pressure during periods of extinction of the discharge. Difficulties are then experienced at each restriking of the discharge after an extinction. Moreover, with electric discharge lamps wherein a high pressure gas filling is utilized, the filling is always at a high pressure and the difficulty of repeated restriking of the discharge is experienced whatever the rate of flashing.

The difficulties of restriking the discharge mentioned above can, in both cases, be mitigated and the restrikin voltage considerably reduced,

by the use of an auxiliary discharge. Thus, one 1 form of high pressure gas or vapor filled discharge lamp suitable for use in accordance with our invention, is provided with electrodes for producing an auxiliary discharge within the lamp, in addition to the main discharge. This auxiliary discharge occurs between one of the main electrodes and an auxiliary electrode mounted in proximity to the latter Within the lamp envelope. Th ionization produced in the main discharge path by the auxiliary discharge facilitates the restrikin of the main discharge. Lamps of this type will hereinafter be referred to as auxiliary discharge high pressures electric discharge lamps.

The principal object of our invention is to provide a new and improved circuit arrangement for producing repeated flashes of light by means of an auxiliary discharge high pressure electric discharge lamp.

A more specific object or our invention i to provide an improved apparatus for use in combination with an auxiliary discharge high pressure electric lamp for maintaining a continuous auxiliary discharge within the lamp during operation of the apparatus, the intensity of the auxiliary discharge being varied depending upon whether or not the lamp is extinguished,.in order to provide economy of operation.

In accordance with our invention, the apparatus for producing repeated flashes of light by means of an auxiliary discharge high pressure lamp comprises switch means for alternately striking and extinguishing the main discharge in the lamp so as to produce the desired flashes of light, means for maintaining an auxiliary discharge continuously Within the lamp during operation of the apparatus, and a boosting circuit arranged to increase the auxiliary discharge current automatically Whenever the switch means is operated to restrike the main discharge.

For further objects and advantages and for a better understandin of the invention, attention is now directed to the following description and accompanying drawing. The features of the invention believed to be novel will be more fully pointed out in the appended claims.

The single figure of the drawing is a schematic representation showing an auxiliary electrode high pressure electric discharge lamp in combination with a circuit arrangement embodying our invention.

Referring to the drawing, the discharge device or flash lamp i comprises a glass envelope 2 having a pair of main electrodes 3 and i sealed into opposite ends thereof. The envelope 2 contains an ionizable medium in the form of a gas such as argon, xenon, neon, krypton, or hydrogen, or mixtures of gases and metallic vapors. An auxiliary startin electrode 5 is mounted within the envelope 2 in proximity to the main electrode 4.

The circuit arrangement comprise a trans former 6 having a primary winding 1 with input terminals 8 and 9 adapted to be connected to a commercial source of alternating current, and a pair of secondary windings Id and H. Across the secondary winding Id are connected in series the main electrodes 3 and 4 of the lamps, a stabilizing impedance which has been illustrated in the form of a current limiting resistor l2, and the normally open contacts is of a relay id. The operating coil id of relay is likewise connected across secondary winding 6 c in series with a signalling key l6.

Secondary winding H has a common connection to one side of winding I0 and is poled so as to provide a maximum voltage, that is, the sum of the voltages induced in both windings, between the lower terminal of winding l8 and the upper terminal of winding H. In other words, the secondary voltages diverge from the common point to the outer terminals on both sides. The upper terminal of winding H is connected, in series with a pair of impedances which have been illustrated as inducta-ncesl1, and ill, to the auxiliary electrode 5, of lamp i. Inductance i8 is shunted by the normally open contacts is of a relay 20 whose operating coil 2l1 is connected in parallel with the operating coil is of relay it. Thus, the operating windings or both relays i4 and 20 are connected, in series with the signalling key I6, across secondary winding iii. The function of the additional relay 22, whose normally closed contacts 23 are serially included in the shunting circuit across inductance i8, willbe considered later.

The transformerratios are such, in relation to the alternating current source, that the voltage across secondary winding 10 is suflicient to maintain the lamp in operation whenthe main discharge has been established. In conjunction with the current limiting resistor l2, the main dischargecurrent may be established at a value whichv would overload the lamp if operated continuously. The voltage across the secondary windings l0 and H in series is such that when, in the initial starting of the apparatus, it is applied in full between the main electrode 4 and the auxiliary electrode 5, it is sufficient to cause the auxiliary discharge to be established in the startingof the lamp from the cold condition and to be maintained throughout the operation of the apparatus. 7

The inductances H and I8 provide part of the stabilizing impedance iorthe auxiliary discharge, the remainder being provided by-the current limiting resistor 12. The values of these imped-ances are such that all three together maintain the auxiliary discharge current inoperation at approximately the minimum required to maintain a stable auxiliary discharge while with inductance H and resistor l2 alone a greatly increased auxiliary discharge current is obtained.

In the operation of theapparatus, after the auxiliary discharge has been established and, in the case of a metal vapor been run up to its full operating pressure, signalling is effected by operation of the key I6. When the key is open, relays l4 and ZU-arede-energized and their contacts open. The opening of contacts l3 breaksthe lamp circuit and extinguishes the main discharge while the opening of contacts t9 places all three impedances in series with the auxiliary discharge; that-is, inductance i8 is inserted in the auxiliary discharge circuit in addition to inductance l1 and resistor !2. This causes the auxiliary discharge to operate at its minimum value of current when the main discharge is extinguished. When the signalling key it is depressed, the relays are energized and their contacts closed. The closing of contacts 23 applies the operating voltagebetween the main electrodes of the lamp while the closing of contacts i9 short-circuits the inductance l8- and boosts the auxiliary discharge current. As a result, the restriking of the discharge between the main electrodes of the lamp is. effected reliably.

It will be understood that the boostmeans which has been illustrated and which consists lamp, the filling has iii 4 simply of an arrangement for modifying an inipedance which lies in series with the auxiliary discharge may take other forms than that illustrated, and other electrical or mechanical linkages with the switch means or signalling switch It may be provided.

The effect of the increased auxiliary discharge current during. the periods of restrilzing the main discharge is to produce increased ionization in the main discharge path. This effect can be turned to advantage in difierent ways. Thus, in the simplest case it can be used merely to insure more reliable or more rapid restriking of the main discharge even in cases where the lower value of auxiliary discharge current, cbtai g during the periods of extinction of the m charge, is normally sufficient to ca se rest Alternatively, it can be applied to enable the voltage necessary to cause the main discharge to restrike, to be reduced to a value below that necessary to insure restriking at the lower value of auxiliary discharge current. Again, in other cases, it may be arranged that the 10 P va ue of auxiliary discharge current is the n nimum required to maintain stable auxiliary discharge. In general, this value is appreciably lower than that required to insure reliable restrilzing. In this way, greater economy of operation can be achieved; and, moreover, light emitted by the lamp during periods of extinction of the main discharge, which light comes wholly from the auxiliary discharge, is red ced to a minimum and does not detract from the clarity and sharpness of the flashes.

As another advantage, the increased ionization resulting from the boosted auxiliary discharge current in the operation of the arrangement, may render practical the use of a lamp in which the auxiliary discharge path is well separated from the main discharge path. With such a lamp, the light from the auxiliary discharge can be more readily obscured in the operation of the apparatus and reliable restrihing of the main discharge is still obtained.

In the preferred embodiment of the invention. illustrated in the drawing, the additional relay 22 permits boosting the auxiliary discharge current during the first part only of each period of operation of the main discharge after restrik ing. Relay 22 is of the time delay type and has its normally closed contacts 23 inserted in series with contacts IS in the shunt circuit across in ductance l8, and its operating coil 2 1 connected in parallelwith those of relays M and 2c. The time delay relay contacts would then open a short interval of time after the striking of the main discharge and reduce the auxiliary discharge current to its minimum value during the occurrence of the main discharge. In this way, reliable restrilzing of the main discharge can still be insured and yet greater economy of operation obtained.

In one actual construction of the arrangement illustratedin the drawing, the lamp 4 was a high pressure mercury vapor electric discha" lamp having anapproximately spherical quartz envelope of internal diameter 9 cm. and provided with main electrodes consisting of tungsten rods sealed into the envelope at diametrically opposite points. The are gap between the main electrodes at the, center of the envelope was approximately 1.0 mm. The auxiliary electrode 5was a tungsten rod sealedinto the envelope with its inner end spaced 3 mm. from one of the main electrodes,

the lamp being arranged with this main electhe main electrodes.

The transformer 6 was such that, when operated from a 400-volt, 50-cycle supply, the voltage and I8, values of 97 and 290' millihenrys, respectively. The current in the main discharge during flashes was approximately 150 amperes and key.

While a certain specific embodiment has been shown and described, it will of course be understood that various modifications may be made without departing from the invention. Moreover, while the embodiment which has been described is adapted for alternating current operation, it will be understood that no limitation to such operation is implied and that the apparatus may readily be adapted to operate with direct current. The appended claims are, therefore, intended to cover any such modifications coming within the true spirit and scope of the invention.

What we claim as new and desire to secure by Letters Patent of the United States is:

1. In combination, a high pressure metal vapor discharge device comprising an envelope containing a pair of main discharge supporting electrodes, a vaporizable metal filling, and an auxiliary electrode mounted in proximity to one of said electrodes for ionizing the main discharge path, a first voltage source, a stabilizing impedance, and a main discharge circuit comprising said main electrodes connected in series with said stabilizing impedance across said first source, a second voltage source, a current limiting impedance and an auxiliary ionizing circuit comprising said auxiliary electrode and said one main electrode connected in series with said current limiting impedance across said second source, said second voltage source in conjunction with said current limiting impedance being proportioned to maintain a minimum ionization within said path in order to maintain the device active, and means short circuiting part of said current limiting impedance in said auxiliary circuit upon energization of said main circuit thereby to increase said ionization and facilitate striking of the main discharge.

2. In combination, a high pressure metal vapor discharge device comprising an envelope containing a pair of main discharge supporting electrodes, a vaporizable metal filling, and an auxiliary electrode mounted in proximity to one of said electrodes for ionizing the main discharge path, a first voltage source, a stabilizing impedprising said auxiliary electrode and said one main electrode connected in series with said current limiting impedance, across said second source, said second voltage source in conjunction with said current limiting impedance being proportioned to maintain a minimum ionization within said path in order to maintain the device active, and a pair of normally open switching means, one of said means being serially included in said main circuit, and the other being simultaneously operable with the first and connected to short circuit part of the current limiting impedance in said auxiliary circuit, thereby to produce increased ionization in said path to facilitate striking of the main discharge.

3. In combination, a high pressure metal vapor discharge device comprising an envelope containing a pair of main discharge supporting electrodes, a vaporizable metal filling, and an auxiliary electrode mounted in proximity to one of said main electrodes for ionizing the main discharge path, an alternating voltage source, transforming means connected across said source and providing a secondary voltage diverging from a common point on both sides to two outer terminals, a stabilizing impedance, a main discharge circuit comprising said one main electrode connected in series with said stabilizing impedance to one of said outer terminals, and the other main electrode connected to said common point, a current limiting impedance, an auxiliary ionizing circuit comprising said auxiliary electrode connected in series with said current limiting impedance to the other of said outer terminals, said transforming means between said common point and said other outer terminal in conjunction with said current limiting impedance being proportioned to maintain a minimum ionization within said path in order to maintain the device active, and means short circuiting part of said current limiting impedance in said auxiliary circuit upon energization of said main circuit in order to increase said ionization and facilitate striking of the main discharge.

4. Signalling apparatus comprising a high pressure metal vapor discharge device having an envelope containing a pair of main discharge supporting electrodes, a vaporizable metal filling, and an auxiliary electrode mounted in proximity to one of said main electrodes, an alternating voltage source, transforming means connected across said source and providing a secondary voltage diverging from a common point on both sides to a pair of outer terminals, a stabilizing impedance, a main discharge circuit comprising said one main electrode connected in series with said stabilizing impedance to one of said outer terminals, and the other main electrode connected to said common point, a current limiting impedance, an auxiliary ionizing circuit comprising said auxiliary electrode connected in series with said current limiting impedance to the other of said outer terminals, said transforming means between said common point and said other outer terminal in conjunction with said current limiting impedance being proportioned to maintain a minimum ionization within said path in order to maintain the lamp active, and switching means for operating said lamp comprising a first pair of normally open contacts inserted between said other main electrode and said common point, a second pair of normally open contacts shunted across part of said current llmiting impedance, and a third pair of normally closed contacts serially included with said second pair in shunt across said current limiting impedance, said switching means being adapted to close said first two pairs of contacts simultaneously thereby to complete said main circuit and to increase simultaneously the ionization in said path to facilitate striking of the main disreduce the current in said auxiliary circuit, after.

the main discharge has started, to the minimum ionization value.

ANTHONY Di COOPER. EVAN H. NELSON. ANTHONY H. WILLOUGHBY.

References, Cited. in the file a! this patent UNITED STATES BATENTS- Number Name Date Erickson i....-....- Oct. 16, 193 Bird wihhahuh June 8, 1937 Inman Oct. 31,1939 Germeshausen Apr. 30,1948 Hinman i- Oct. 19, 1948 Francis Dec. 21, 1948 Lord: "A May 23, 1950 Kaphm Nov. 21, 1950 

